Changes to make 29k function calls work better at Adobe.

Changes to make 29k function calls work better at Adobe.

* am29k-tdep.c (_initialize_29k):  Make it possible for the
user to set and query the address where function calls into the
inferior write a small scratch routine.  `set call_scratch_address'
* inferior.h (PC_IN_CALL_DUMMY):  Fix fencepost error.
* remote.c (remote_prepare_to_store): Only fetch regs if they are
not already cached validly.